<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width: 150px;
            height: 15px;
            border: 1px red solid;
            padding: 1px;
            border-radius: 7px;
        }
        .x{
            width: 50%;
            background-color: red;
            height: 100%;
            transition: all .5s ease .2s;
            border-radius: 7px;
        }
        .box:hover .x{
            width: 100%;
            height: 50px;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="x"></div>
    </div>
</body>
</html>